747-400 FMC Perf Init Fuel "SENSED" Annunciation
 

I was wondering if someone could explain the following:

On the ground, when any EEC Test Switch on a CF6-powered 747-400 is selected on, the FMC Perf Init page FUEL data switches from CALC to SENSED in a few seconds (after the EECs are powered up via the test switches).

The manuals say that, with engines running, if Fuel Flow transmitter data becomes inop for two minutes, the FMC uses SENSED (FQIS) data. However, the Fuel Flow data is actually being enabled by switching on the EECs (FF transmitters send data to the FMCs via the EECs (unlike RB211s and PW4000s). So I see no reason for the SENSED annunciation to appear (and so quickly)

Thanks
Regards
NSEU